Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 43.5	$ 36.5
Restricted cash	0.1	10.5
Accounts receivable, net	68.2	67.9
Accounts Receivable, Allowance for Credit Loss, Current	3.2	0.4
Inventories	8.2	10.4
Taxes applicable to subsequent years	20.0	77.5
Regulatory assets, current	20.9	19.7
Income Taxes Receivable, Current	11.6	23.6
Prepayments and other current assets	5.4	7.6
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	22.3
Total current assets	177.9	276.0
Property, plant & equipment:
Property, plant & equipment	1,805.9	1,701.9
Less: Accumulated depreciation and amortization	(402.8)	(362.6)
Property, plant and equipment, net of depreciation	1,403.1	1,339.3
Construction work in process	112.0	106.3
Total net property, plant & equipment	1,515.1	1,445.6
Other non-current assets:
Regulatory assets, non-current	177.0	173.8
Intangible assets, net of amortization	17.8	19.3
Other non-current assets	19.7	20.0
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	0.0	1.1
Total other non-current assets	214.5	214.2
Total assets	1,907.5	1,935.8
Current liabilities:
Current portion of long-term debt	90.2	283.8
Accounts payable	54.8	72.6
Accrued taxes	83.3	79.3
Accrued interest	18.8	11.4
Security deposits	18.7	20.7
Regulatory liabilities, current	19.8	27.9
Other current liabilities	21.6	21.2
Liabilities Held for Sale, Current	0.0	9.0
Total current liabilities	307.2	525.9
Non-current liabilities:
Long-term debt	1,392.9	1,223.3
Deferred taxes	173.4	133.7
Taxes payable	2.9	81.1
Regulatory liabilities, non-current	220.5	243.6
Pension, retiree and other benefits	69.0	79.9
Other deferred credits	18.2	11.8
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0.0	8.4
Total non-current liabilities	1,876.9	1,781.8
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0	0.0
Other paid-in capital	2,468.8	2,370.7
Accumulated other comprehensive income	(3.6)	(3.6)
Retained Earnings (Accumulated Deficit)	(2,741.8)	(2,739.0)
Total common shareholder's equity	(276.6)	(371.9)
Total liabilities and shareholder's equity	$ 1,907.5	$ 1,935.8
Common Stock, Shares Authorized	1,500	1,500
Common stock, shares issued	1	1
Par value common shares (in USD per share)	$ 0.01
Subsidiaries [Member]
Current assets:
Cash and cash equivalents	$ 26.1	$ 10.8
Restricted cash	0.1	10.5
Accounts receivable, net	69.2	70.9
Accounts Receivable, Allowance for Credit Loss, Current	3.2	0.4
Inventories	8.2	10.4
Taxes applicable to subsequent years	19.7	77.4
Regulatory assets, current	20.9	19.7
Income Taxes Receivable, Current	32.8	35.7
Prepayments and other current assets	6.7	10.8
Total current assets	183.7	246.2
Property, plant & equipment:
Property, plant & equipment	2,409.5	2,333.6
Less: Accumulated depreciation and amortization	(1,025.2)	(1,012.7)
Property, plant and equipment, net of depreciation	1,384.3	1,320.9
Construction work in process	109.4	104.5
Total net property, plant & equipment	1,493.7	1,425.4
Other non-current assets:
Regulatory assets, non-current	177.0	173.8
Intangible assets, net of amortization	16.8	18.2
Other non-current assets	19.3	19.6
Total other non-current assets	213.1	211.6
Total assets	1,890.5	1,883.2
Current liabilities:
Current portion of long-term debt	0.2	179.8
Accounts payable	53.7	74.4
Accrued taxes	84.3	79.4
Accrued interest	6.0	1.4
Security deposits	18.5	20.6
Regulatory liabilities, current	19.8	27.9
Other current liabilities	28.7	16.3
Total current liabilities	211.2	399.8
Non-current liabilities:
Long-term debt	573.9	434.6
Deferred taxes	172.1	158.1
Taxes payable	2.8	82.3
Regulatory liabilities, non-current	220.5	243.6
Pension, retiree and other benefits	69.0	79.9
Other deferred credits	10.7	11.5
Total non-current liabilities	1,049.0	1,010.0
Commitments and contingencies
Common shareholder's equity:
Common stock	0.4	0.4
Other paid-in capital	724.4	617.0
Accumulated other comprehensive income	(34.7)	(36.9)
Retained Earnings (Accumulated Deficit)	(59.8)	(107.1)
Total common shareholder's equity	630.3	473.4
Total liabilities and shareholder's equity	$ 1,890.5	$ 1,883.2
Common Stock, Shares, Outstanding	41,172,173	41,172,173
Common Stock, Shares Authorized	50,000,000	50,000,000
Par value common shares (in USD per share)	$ 0.01